1. Field of the Invention
The present invention relates to a containerized refrigerant comprising a refrigerant in a portable disposable container, which is used when a refrigerant is charged or recharged into a cooling apparatus such as an automobile air conditioner, a refrigerator, and a general air conditioner, and relates to a method for maintaining the purity of the refrigerant in the portable disposable container. In particular, the present invention relates to a containerized refrigerant comprising a refrigerant in a disposable container, by which problems such as degradation of the purity of the refrigerant and corrosion of the container during storage, which occurred in conventional containerized refrigerants comprising a hydrogen-containing fluorocarbon in a disposable container, are avoided for a long time, and also relates to a method for maintaining the purity of such a refrigerant.
This application is based on patent application No. Hei 9-92574 filed in Japan on Apr. 10, 1997, the content of which is incorporated herein by reference.
2. Description of Related Art
Conventionally, as refrigerants in cooling apparatuses and refrigerating apparatuses, dichlorodifluoromethane (commonly called CFC12), chiorodifluoromethane (commonly called HCFC22), and the like are widely used in large quantities. Particularly, in the field of automobile air conditioners (in-car air conditioners), since the amount of the refrigerant to be charged is relatively small, a containerized refrigerant in a small disposable can, such as a disposable can for a refrigerant having a volume of about 1 liter or less which is filled, for example, with CFC 12, is common on the market for recharging following leakage.
In the case, for example, of CFC12 used as a refrigerant for refrigerators and HCFC22 used as a refrigerant for air conditioners, on the other hand, since the initial charge or recharge amount is relatively large, the refrigerant is filled into strong portable refillable containers which have no welds or seams. Since these large portable containers are expensive to produce, after being used, as a general rule, they are returned to the refrigerant suppliers and are refilled to be used repeatedly. However, the rate of recovery of the containers has gradually declined, and it has become a factor in increasing the cost of the containerized refrigerants. Thus, recently, with respect to these large portable containers, attention is increasingly paid to inexpensive welded-type disposable portable containers having valves which do not allow refilling after use.
In recent years, the depletion of the ozone layer in the stratosphere by chlorofluorocarbons (commonly called CFCs) has been brought forward as a serious environmental problem, and the production of chlorofluorocarbons has been discontinued since the end of 1995. Therefore, at present, in the field of automobile air conditioners wherein CFC12 was conventionally used, the use of HFC134a (CH.sub.2 FCF.sub.3) which is one of the hydrofluorocarbons (commonly called HFCs) has superseded the use of CFC12, and similarly, a containerized refrigerant made by filling HFC134a into a small disposable container is becoming common for use in recharging. Although the demand for containerized refrigerants for recharging of refrigerators that use HFC134a has increased, such containerized refrigerants have not yet been put into practical use since the long-term reliability of refrigerators requires a refrigerant of higher quality than that used for automobile air conditioners.
Further, with regard to the above HCFCs, although the deleterious effects on the ozone layer are less than those of CFCs, because of the possibility that the amount of HCFCs will increase due to their being alternatives to CFCs, abolition of the use of HCFCs in principle in 2020 was decided, and the international regulation of total emissions was begun in 1996. Therefore, as an alternative to HCFC22 which is widely used in air conditioners and the like, a refrigerant having an HFC component which falls outside the regulations and whose ozone depleting potential is zero is now being studied.
As a refrigerant composition that can replace HCFC22, there is no single refrigerant that can be used as-is in conventional apparatuses designed for HCFC22, and therefore two-component or three-component HFC-type mixed-refrigerants, the physical properties, etc., of which are adjusted by mixing several components, were developed. However, since most of these mixed refrigerants are non-azeotropic mixtures, these mixed refrigerants filled in a conventional large portable refrigerant container have the problem that during a recharging procedure, the proportions of the components in the mixture at initial dispensing differ from those at later dispensing. Thus, in order to solve this problem and maintain the cooling/refrigerating performance constant at all times, a disposable containerized refrigerant for recharging a high-quality refrigerant is required in which the high-quality refrigerant is containerized in an amount needed for one recharging.
Conventionally, for example, containerized refrigerants for recharging service using CFC12 which has been used for automobile air conditioners, or HFC134a which is currently being used, are charged into an air conditioner in an amount of between 200 and 300 g and are products that can be handled by general consumers. These containerized refrigerants are supplied on the market in small disposable cans which are mass-produced by rolling metal sheets, which costs less. The container of the containerized refrigerant has a structure by which the refrigerant may be dispensed by opening the can by screwing a separately-supplied exclusive-charge-valve into a threaded part of an upper part of the can to cause a built-in needle to pierce a lid plate of the can. After opening, the can cannot be used again.
The structure of the above disposable can is very simple, and when the can is filled with a refrigerant, a liquid refrigerant is generally filled into the can while an upper part of the can is open, and the can is sealed with a lid plate by staking them together ("staking" herein means "fitting the two parts together and causing a plastic flow at the joint"). Accordingly, even if the original refrigerant before filling is of a desirably high quality, in comparison to that in general welded-type portable refrigerant containers, the possibility that the quality is degraded by, for example, contamination with water and organic substances, such as oil components in the filling step, is high and cannot be avoided.
Further, as is shown in FIG. 4, the above disposable can comprises a disposable container body 42 wherein, in order to maintain the hermetic seal, an elastomer packing material 48 is used at at least the part where a lid plate 47 is joined to the disposable can body 42. Furthermore, in some cases, a sealant 46c, for example, of a resin compound is used at a joining part where a bottom plate 46b of the container body is joined to a cylindrical side plate 46a. The packing material 48 and sealant 46c are in contact with the refrigerant for a long time during storage of the containerized refrigerant, and therefore dissolving of organic substances, such as plasticizers, into the refrigerant, thereby increasing the evaporation residue of the refrigerant over time cannot be avoided. Therefore, as the quality standard of conventional refrigerants for recharging automobile air conditioners, the allowable value of the evaporation residue is set to be, for example, 100 ppm by weight or less, which is a relatively lenient value.
Further, during storage of the above containerized refrigerant, particularly when the humidity in the air is high, such as in summer, the following phenomenon is known: in addition to the osmotic pressure of moisture, breathing action due to a change in the internal vapor pressure caused by a change in the temperature of the air allows moisture to penetrate, for example, through the packing material and the seal thereby allowing the moisture concentration of the refrigerant to increase over time, leading to the problem that the quality of the contained refrigerant is inevitably degraded, limiting product life. Therefore, the quality standard for conventional refrigerants for recharging automobile air conditioners restricts the moisture content to 50 ppm by weight or less. It is known that since HCFCs and HFCs contain hydrogen atoms in their molecules, they are particularly high in hygroscopicity in comparison with conventional CFCs.
Further, it is also known that moisture contained in a refrigerant in contact with the metal of a can for a long period of time causes the refrigerant to gradually hydrolyze to produce inorganic acids, such as HCl and HF, thereby not only degrading the quality of the refrigerant, but also possibly causing corrosion or leakage of the can. Accordingly, acid components are also restricted conventionally by the quality standard and are set to 1 ppm or less by weight, which will generally not result in corrosion or the like.
With respect to containerized refrigerants for recharging domestic appliances such as domestic refrigerators and indoor air conditioners, the quality standards are even more stringent to ensure long-term reliability; for example, the moisture is set to be 20 ppm by weight or less, the acid content is set to be 0.2 ppm by weight or less, and the evaporation residue consisting of at least one of the oil content and the organic substance content is set to be 20 ppm by weight or less. Hence, the above small disposable canned refrigerant for recharging automobile air conditioners cannot satisfy the standards for these type of domestic appliances.
As a containerized refrigerant for recharging domestic appliances, one is known in which a refrigerant is contained in a relatively large welded-type disposable portable container having a volume of about 45 liters or less. Although this is widely used not only for recharging but also for initial charging in a production line for refrigerating apparatuses, due to the disposable nature of the container, the material used therein must be inexpensive while meeting minimum specifications and must have a valve structure which physically blocks refilling. This valve has a non-returning float inserted therein. The float is placed at an upper part of the container to allow filling only when the refrigerant is initially filled into the container; after closing the main valve, the float remains lowered, and from then on the dispensing of the refrigerant is made possible only by opening the main valve to generate a pressure difference between the inside and the outside to allow the float to be raised; refilling from the outside is never possible because the inner float is in the closed state. Although in the case of general reusable portable containers, special attention is paid to the sealant or the like for the valve, in the case of disposable containers, inexpensive resin sealant are used and the problem of the sealing properties of the structure of the container remains unsolved. Further, the relatively large welded-type disposable portable containerized refrigerant has a problem in that the purity of the refrigerant is degraded due to increases in moisture, acid content, organic evaporation residue, and the like in the refrigerant for the same reasons as in the above small disposable containerized refrigerant for recharging.